Like interlaced snail trails around a garden, every Tour de France criss-crosses editions from the past, reviving memories good and bad. This week, 10 years on from the Festina drug scandal, the race went through Pontivy, the town that is the home of the former Festina team manager Bruno Roussel while Tuesday's time-trial stage was at Cholet, the first visit the Tour had paid the town since the evening in 1998 when gendarmes came to the stage finish there and arrested Roussel and the Festina team doctor, Erik Rijkaert.

That was the moment the scandal arrived at the Tour. A week earlier, French drugs police had arrested the Festina team's masseur, Willy Voet, at the Belgian border. His stash of erythropoietin, growth hormone and amphetamines had been analysed and now the police were moving in on the men at the centre of the team's drug supply. Roussel confessed two days later that he had set up organised doping within the squad, funded by cash siphoned from prize money and wages, and on July 17 the world No1-ranked team was thrown off the Tour.

The impact on the Tour and those around it was massive. The race organiser, Jean-Marie Leblanc, aged visibly in the next 10 days as the Tour fell apart amid sit-down protests from the riders and police raids, with teams and riders quitting as the sport was forced to confront the reality of drug taking in a public arena.

Like the death of Tom Simpson from amphetamines in 1967, Festina changed the course of cycling but, unlike the British champion's demise, the ramifications outside the two-wheeled world were also immense. For the first time in a single major sport, systematic doping at the highest level had been exposed. For the first time it became evident that doping led not merely to positive tests but potentially to the collapse of an entire event.

The chaos on that Tour was followed by an International Olympic Committee Congress in February 1999 and led to the foundation of the World Anti-Doping Agency. The Tour had also shown the need for a test for erythropoietin, the red-blood-cell-boosting hormone that the team were using in industrial quantities because it was undetectable. The test eventually came through in time for the Sydney Olympics in 2000.

Drug testing moved forward in another way, post-Festina. Confronted by the abuse of undetectable substances on such a colossal scale, the French cycling authorities moved quickly to bring in "lateral" testing, in which various blood parameters among cyclists are tested four times a year. This system has developed into the much-vaunted introduction this year by the UCI of "blood passports", a system which has yet to produce apparent results. Festina marked the first time a national police force had become so heavily involved in policing doping. Campaigners such as the Italian Sandro Donati had been pointing out that the volumes of banned drugs being abused in high-level sport meant organised crime would be involved, hence the French police's decision to treat the episode as a drug trafficking case. Since the Festina affair, European police forces, notably the Italians, have raided major sports events such as the Giro d'Italia and the Winter Olympics, and made regular seizures of banned drugs.

Cycling has moved forward since the days when teams openly carried refrigerators of EPO to major events, and "Belgian pot" was bartered at races. But opinions remain divided on the efficacy of the fight against doping given recent scandals. "It's been 10 years since the Festina scandal but 10 years is simply not long enough to change a system which is so deep-rooted," said the French anti-doping campaigner Jean-Pierre de Mondenard. "It will take at least 25 years for attitudes towards doping to radically change.

"In the 1960s riders moved from one amphetamine to the next as they became detectable, and it's no different now. There are around 20 products which remain undetectable and can be used to cheat. If you have undetectable substances on the market, they're going to be used."

The former Festina manager Bruno Roussel feels there has been a sea-change, at least in France, something that is borne out whenever one speaks to almost any French cyclist racing today. "After 1998, a lot of information was provided on doping. A whole generation which was 12 or 13 years old has been made aware of the dangers. There has been a lot of work at official level, and the media have stigmatised doping as cheating and damaging to health. Today, anyone who is properly looked after should be well enough informed, supported and watched over that they do not get into it. Those who do get into it are genuinely cheating to get what they want: money, glory and medals."

The clear-out: major doping scandals since Festina

2002 Johan Muehlegg of Spain and Larissa Lazutina of Russia, the latter 14 times a world championship medalist, are stripped of cross-country skiing gold medals after testing positive for the blood booster darbepoetin in the Winter Olympics.

March 2003 197 Former East German athletes file claims for medical assistance to counter the side effects of their country's systematic doping programme that ended with the fall of the Berlin Wall in 1989.

September 2003 The BALCO factory in Burlingame, California, is raided. Banned drugs are seized along with a list of athletes in baseball, athletics, and NFL to whom drugs have been supplied. Among those later banned is Britain's European 100m gold medalist Dwayne Chambers.

August 2004 Sprinters Kostas Kenteris and Ekaterina Thanou withdraw from the Olympic Games in Athens after evading a drugs test. Both are later banned.

August 2005 Allegations that seven-times Tour winner Lance Armstrong tested positive for EPO in 1999 are published in l'Equipe; the ICU rules that Armstrong does not have a case to answer.

June 2006 Operacion Puerto blood-doping investigation nets a dozen top cyclists including Jan Ullrich and Ivan Basso; they are thrown out of the Tour the night before the start.